Zyrtec is one of the few antihistamines that do not cause drowsiness for most dogs, though there are some exceptions. If Zyrtec makes your dog sleepy, try giving it to them before bedtime to see if that helps their energy levels during the day.
The most common side effects of antihistamines in dogs include sedation and drowsiness. This is more commonly noticed with first-generation antihistamines such as diphenhydramine (Benadryl®). Newer generation antihistamines such as cetirizine (Zyrtec® or Reactine®) have less of a sedating effect.
Cetirizine does not typically cause any side effects. Vomiting and increased salivation have been observed in some dogs. At high doses, sleepiness has been reported in small dogs and cats. Any side effects that are severe or worsen should be reported to your veterinarian.
Antihistamines are usually safe but can make some dogs drowsy and others hyperactive. OTC antihistamine preparations may contain other ingredients such as decongestants that are not safe for dogs. Read the label carefully to ensure that the product only contains antihistamine.
You can safely give Zyrtec to your dog up to 20 mg per day.
Pet allergy relief
ZYRTEC® starts working at hour 1 and stays strong day after day, so you can reduce your cat and dog allergy symptoms.
You may be wondering whether Claritin or Zyrtec is the best pet allergy medicine—but which antihistamine works best for you depends on the severity of your symptoms. For example, a person with a mild allergy to cats or dogs may do well with Claritin. Another person with more severe allergies may do better with Zyrtec.
The dose is 5–20 mg/dog once daily. cetirizine (Zyrtec®) – also second gen. It is available as 10 mg tablets and either 1 mg/ml or 10 mg/ml oral solution. The dosage is 5–20 mg/dog once daily.
If your dog is prescribed antihistamines you will need to try them for 2-3 weeks to see if it helps. If it doesn't, you'll need to stop giving it to your dog and try another until you find one that works, following the advice of your vet.
Here's the recommended Zyrtec dosage for dogs based on their weight: Less than 10 pounds: 2.5 milligrams (half of a 5-milligram pill or a quarter of a 10-milligram pill) 10–50 pounds: One 10-milligram tablet. 50+ pounds: Up to two 10-milligram tablets.
Since the effects of Zyrtec last 24 hours, drowsiness can hit at any time. Avoid alcohol and be careful about driving if the med hits you with the sleepies, per the Zyrtec site.
Zyrtec is 3.5 times more likely than Claritin to cause sedation, particularly when used at dosages higher than 10mg/day. However, Zyrtec is still much less sedating than older antihistamines such as promethazine.
Sedating antihistamines cause sedation as they are highly lipid soluble and readily cross the blood brain barrier. This sedating activity is sometimes used in managing conditions such as eczema where sleep maybe disturbed due to pruritus.
Antihistamines, mainly used to treat symptoms of hay fever or other allergies, can induce drowsiness by working against a chemical produced by the central nervous system (histamine). These medications can be useful in certain situations, such as for treating sleeplessness related to travel.
Cetirizine (Zyrtec) ¼ - ½ mg per pound (one 10mg tab per 30-40 lbs) twice daily. Loratadine (Claritin): ¼ mg per pound (half of a 10mg tablet per 20 lbs) once daily. Clemastine (Tavist-1, Antihist-1): 0.02mg per pound (one 1.34mg tablet per 65lb dog) twice daily.
Toxicity to pets
When accidentally ingested by dogs and cats, antihistamine poisoning can result in clinical signs of severe agitation, lethargy, sedation, aggression, abnormal heart rate, abnormal blood pressure, vomiting, diarrhea, inappetance, seizures, respiratory depression, and even death.
One of the side effects of Benadryl is drowsiness, which helps to calm anxious dogs. The Merck Veterinary Manual states that diphenhydramine may relieve symptoms of mild-to-moderate anxiety in pets associated with travel. It also may help relieve motion sickness.
Dosing Information of Cetirizine for Dogs and Cats
Cetirizine is dosed in dogs at 0.5 mg per pound (1 mg/kg) orally once to twice daily.
DO NOT USE ALLEGRA D IN PETS. Fexofenadine is also available an oral suspension that contains xylitol (NOTE: Xylitol may be toxic in dogs). The human oral suspension is not recommended for use in pets.
Best treatment: Antihistamines
Antihistamines are commonly used to treat dog allergies. Their histamine-blocking quality tackles airborne allergens and reduces symptoms in your pup. The safest over-the-counter options for your dog include Benadryl, Zyrtec, Claritin, and Allegra.
Clemastine Fumarate. Also recommended as an antihistamine for dogs is clemastine fumarate. It is one of the most effective antihistamines for dogs with itchy skin.
Allergies in dogs are different than allergies in people. Histamines cause upper respiratory allergies in people, whereas cytokines (not histamines) cause itchy skin in dogs. For dogs with underlying allergies, antihistamines don't control the cytokines (signaling proteins) that cause inflammation and itch.
ZYRTEC 10 mg film-coated tablets
Swallow the tablet whole, with a glass of water. You can divide the tablet into two equal doses.